Electrosurgical instrument

ABSTRACT

Electrical instrument for applying radiofrequency and/or microwave frequency energy to tissue, comprising: a distal part comprising an instrument tip for applying radiofrequency and/or microwave frequency energy to tissue, the instrument tip comprising first and second conductive elements; a coaxial feed cable comprising an inner conductor, a tubular outer conductor coaxial with the inner conductor, and dielectric material separating the inner and outer conductors, the coaxial feed cable being for conveying radiofrequency and/or microwave frequency energy to the distal part; wherein: the inner conductor is electrically connected to the first conductive element and the outer conductor is electrically connected to the second conductive element through a rotatable connection between the distal part and the coaxial feed cable that allows rotation of the distal part relative to the coaxial feed cable; and the instrument comprises an actuator for rotating the distal part in a first rotational direction relative to the feed cable.

FIELD OF THE INVENTION

The present invention relates to an electrosurgical instrument forapplying radiofrequency energy and/or microwave frequency energy tobiological tissue. In particular, the present invention relates to suchan electrosurgical instrument in which an instrument tip of theinstrument is rotatable relative to a coaxial feed cable of theinstrument. In practice, the present invention may be passed through aninstrument channel of a surgical scoping device, such as an endoscope,gastroscope, neuroscope, laparoscope, etc. Rotation of the instrumenttip at the distal end of the endoscope may be controlled at the proximalend of the endoscope.

BACKGROUND OF THE INVENTION

Electrosurgical instruments are instruments that are used to deliverradiofrequency and/or microwave frequency energy to biological tissue,for purposes such as cutting biological tissue or coagulating blood.Radiofrequency and/or microwave frequency energy is supplied to theelectrosurgical instrument using a transmission line, such as a coaxialcable, waveguide, microstrip line or the like.

It is know to use coaxial cables to deliver microwave energy along aninstrument channel of a surgical scoping device to an electrosurgicalinstrument at the distal end of that channel. Such coaxial feed cablesnormally comprise a solid or flexible cylindrical inner conductor, atubular layer of dielectric material around the inner conductor, and atubular outer conductor around the dielectric material. The dielectricand/or outer conductor can be multi-layer structures.

An electrical connection is generally formed between the inner and outerconductors of the coaxial feed cable and corresponding conductorelements of an instrument tip (also referred to herein as an endeffecter) by soldering a conductor such as a piece of wire or foil tothe inner/outer conductor and to the corresponding conductor element.Radiofrequency energy and/or microwave frequency energy can thus becommunicated from the coaxial feed cable to the instrument tip fordelivery into the biological tissue.

Electrosurgical instruments have been used in conjunction withendoscopes, for example to cut or ablate a small portion of tissue inthe gastrointestinal (GI) tract. In this context, the electrosurgicalinstrument is passed through an instrument channel of the endoscope, sothat the instrument tip protrudes from the distal end of the endoscopewhere it can be brought into contact with the GI tract.

SUMMARY OF THE INVENTION

The present inventors have realised that in some electrosurgicalprocedures it is advantageous to rotate an instrument tip of anelectrosurgical instrument, for example an instrument tip of anelectrosurgical instrument that has been passed through the instrumentchannel of a surgical scoping device. Typically, such an electrosurgicalinstrument has a flexible shaft that is lies along the length of theinstrument channel and terminates at the instrument tip at its distalend. The flexible shaft can be a sleeve that defines a lumen forcarrying components of the device, such as a coaxial cable for conveyingRF and/or microwave energy, fluid for delivery or cooling at theinstrument tip, control lines for actuating movable parts of theinstrument tip, etc.

In some cases rotation of the instrument tip can be achieved by rotatingthe entire electrosurgical instrument around a central axis thereof.However, it can be difficult to control the orientation of theinstrument tip when rotating the whole electrosurgical instrument,particularly if the flexible shaft or other components are fixed at theproximal end of the device. For example, rotation of the coaxial cablemay be restricted by its connection to an electrosurgical generator.

In practice, friction between the inner surface of the instrumentchannel and the shaft resists rotation of the shaft, which can cause theshaft to twist along its axis. Accordingly, it may not be possible toachieve 1:1 rotation due to the build up of torque. The resistanceexperienced by the shaft may increase with length of the device,especially if the tolerances are tight. For example, a 1.8 m longcolonoscope with a 2.8 mm diameter instrument channel carrying a shafthaving an outer diameter of 2.6 mm. This effect may be more pronouncedif the shaft conveys multiple components which give it an irregularcross-sectional shape.

The present inventors have realised there is a need for anelectrosurgical instrument in which the rotational orientation of aninstrument tip (or end effecter) of the instrument can be controlledindependently of the rotational orientation of the flexible shaft.

The present inventors have realised that this can be achieved byproviding an electrosurgical instrument in which there is a rotatableconnection between a coaxial feed cable and an instrument tip of theinstrument (or the end effecter), wherein the rotatable connectionallows rotation of the instrument tip relative to the coaxial feed cablewhile maintaining the necessary electrical connections to enablemicrowave and RF energy delivery, and by providing means for rotatingthe instrument tip relative to the coaxial feed cable. The coaxial feedcable may be contained, e.g. fixed within a flexible sleeve. The meansfor rotating can act to rotate the instrument tip relative to, e.g.around an axis of, the flexible sleeve.

According to a first aspect of the present invention there is providedan electrosurgical instrument for applying radiofrequency energy and/ormicrowave frequency energy to biological tissue, the instrumentcomprising: a distal part comprising an instrument tip for applyingradiofrequency energy and/or microwave frequency energy to biologicaltissue, wherein the instrument tip comprises a first conductive elementand a second conductive element; a coaxial feed cable comprising aninner conductor, a tubular outer conductor coaxial with the innerconductor, and a dielectric material separating the inner and outerconductors, the coaxial feed cable being for conveying radiofrequencyenergy and/or microwave frequency energy to the distal part; wherein:the inner conductor is electrically connected to the first conductiveelement and the outer conductor is electrically connected to the secondconductive element through a rotatable connection between the distalpart and the coaxial feed cable that allows rotation of the distal partrelative to the coaxial feed cable; and the instrument comprises anactuator for rotating the distal part in a first rotational directionrelative to the coaxial feed cable

With the electrosurgical instrument according to the first aspect of thepresent invention, the rotational orientation of the instrument tip canbe controlled by using the actuator to rotate the distal part (whichcomprises the instrument tip) relative to the coaxial feed cable. Thus,the rotational orientation of the instrument tip can be precisely andeasily controlled, which is advantageous for many types ofelectrosurgical procedure.

The instrument tip may have any suitable configuration for deliveringthe RF and/or microwave energy. In an embodiment, the instrument tip mayhave a fixed geometry, such as a flat spatula or blade, on which thefirst conductive element and second conductive element are arranged todeliver the RF and/or microwave energy into biological tissue. Inanother embodiment, the instrument tip may comprise an end effecterhaving an adjustable geometry. For example, the end effector may be anyone of forceps (i.e. a pair of opposed jaws that can open and close),scissors, retractable snare, etc.

A rotatable connection may mean any connection between the coaxial feedcable and the distal part that allows rotation of the distal partrelative to the coaxial feed cable while maintaining the electricalconnections between the inner conductor and the first conductive elementand between the outer conductor and the second conductive element.

Rotation of the distal part means rotation of the distal part around acentral axis of the distal part.

Rotation of the distal part relative to the coaxial feed cable meansthat the distal part can rotate while the coaxial feed cable does notrotate or twist, i.e. while the coaxial feed cable remains stationary.

A rotational direction may mean rotation in either a clockwise ofanticlockwise (counter-clockwise) direction.

An electrical connection between two parts means that an electricalsignal can be communicated from one of the parts to the other part. Itmay mean that the two parts are directly connected. Alternatively, itmay mean that the two parts are indirectly connected, whereby theelectrical signal is communicated between the two parts via a thirdpart.

The inner conductor may be solid. The term solid may mean that the innerconductor is a uniform single piece, for example a single wire.Alternatively, the term solid may mean that the inner conductor isformed from a plurality of wires or fibres arranged or packed together,for example as a braid, to form the inner conductor.

Alternatively, the inner conductor may have a central void or channel,e.g. for conveying other components of the device (e.g. control lines)or for conveying fluid.

In this application, the term distal is used to mean closer to theinstrument tip of the electrosurgical instrument than to an opposite endof the electrosurgical instrument where radiofrequency energy and/ormicrowave frequency energy is input into the electrosurgical instrument.Similarly, the term proximal is used to mean closer to an end of theelectrosurgical instrument where radiofrequency energy and/or microwavefrequency energy is input into the electrosurgical instrument than tothe instrument tip of the electrosurgical instrument. Thus, theinstrument tip is at a distal end of the electrosurgical instrument andthe radiofrequency energy and/or microwave frequency energy is inputinto the electrosurgical instrument, e.g. by an electrosurgicalgenerator, at an opposite proximal end of the electrosurgicalinstrument.

An electrosurgical instrument may be any instrument, or tool, which isused during surgery and which utilises radiofrequency or microwavefrequency energy. Herein, radiofrequency (RF) may mean a stable fixedfrequency in the range 10 kHz to 300 MHz and microwave energy may meanelectromagnetic energy having a stable fixed frequency in the range 300MHz to 100 GHz. The RF energy should have a frequency high enough toprevent the energy from causing nerve stimulation and low enough toprevent the energy from causing tissue blanching or unnecessary thermalmargin or damage to the tissue structure. Preferred spot frequencies forthe RF energy include any one or more of: 100 kHz, 250 kHz, 400 kHz, 500kHz, 1 MHz, 5 MHz. Preferred spot frequencies for the microwave energyinclude any one or more of: 915 MHz, 2.45 GHz, 5.8 GHz, 14.5 GHz, 24GHz.

The electrosurgical instrument may be for cutting, ablating orcoagulating tissue or blood, for example.

The electrosurgical instrument according to the first aspect of thepresent invention may have any one, or, to the extent they arecompatible, any combination of the following optional features.

The electrosurgical instrument may be configured for passing through aninstrument channel of an endoscope. For example, the width of thecoaxial feed cable may be less than an inner diameter of the instrumentchannel of the endoscope. The width of the instrument tip may also beless than the inner diameter of the instrument channel, so that theelectrosurgical instrument can be passed through the instrument channelfrom the proximal end to the distal end thereof when the endoscope is insitu in the gastrointestinal (GI) tract of a person. The coaxial feedcable may thus have a diameter of less than 3.8 mm, preferably less than2.8 mm.

Where the electrosurgical instrument is configured for passing throughthe instrument channel of an endoscope, the actuator preferably enablescontrol of rotation of the instrument tip from a position proximal ofthe proximal end of the instrument channel, so that an operator of theendoscope can control rotation of the instrument tip at the distal endof the endoscope. The actuator may thus include a control portion at aproximal end of the coaxial feed cable.

The coaxial feed cable is preferably a flexible coaxial feed cable, sothat the coaxial feed cable can be passed within a person's GI tract,e.g. in the instrument channel of an endoscope. As discussed above, thecoaxial feed cable may be provided within a flexible sleeve. Theflexible sleeve may form a protective outer surface for the coaxial feedcable. The outer conductor, dielectric material and inner conductor maybe formed on (e.g. as layers inside) the flexible sleeve. In this case,the inner conductor is preferably hollow to form a lumen for othercomponents of the instrument. An inner protective layer may be formed onthe inner surface of the hollow inner conductor. Alternatively, theflexible sleeve may itself define a lumen within which a separatecoaxial cable (e.g. a Sucoform® cable) is carried. Other components ofthe instrument, e.g. control lines, etc. may run parallel with theseparate coaxial cable. The flexible sleeve may define multiple lumensfor carrying respective components.

The distal part may be including a biasing component that resistrotation. Thus, when the distal part is rotated in the first rotationaldirection relative to the coaxial feed cable, the biasing component actsto rotationally bias the distal part in an opposite second rotationaldirection. Upon release the distal part may thus be returned to aninitial rotational orientation by the rotational bias. This mayfacilitate operation of the instrument and may also increase theaccuracy with which the rotational orientation of the instrument tip cancontrolled.

The distal part may be rotationally biased towards a predeterminedrotational position when the distal part is rotated relative to thecoaxial feed cable in the first rotational direction away from thepredetermined rotational position.

A predetermined rotational position may mean a predetermined rotationalorientation, for example an initial rotational position or orientation.

Rotational biasing of the distal part means that the distal part isbiased to rotate around a central axis of the distal part in either aclockwise or anticlockwise (counter-clockwise) direction. In otherwords, a torque is applied to the distal part that acts to rotate thedistal part.

The biasing component (also referred to herein as a biasing element) maybe a piece or a part of the instrument that provides the rotationalbias. The biasing element may be made under compression, or undertension, or under torsion, or otherwise strained by the rotation of thedistal part in the first rotational direction and may thus provide arestoring force that acts to return the distal part to its initialpositon. The biasing element may be made of resilient or elasticmaterial.

The biasing element may rotationally bias the distal part towards apredetermined rotational position when the distal part is rotated in thefirst rotational direction away from the predetermined rotationalposition.

The biasing element may be a spring or a resilient sleeve. Thus, thespring or resilient sleeve may be placed under compression, or undertension, or under torsion, or otherwise strained by the rotation of thedistal part in the first rotational direction.

The resilient sleeve can be a sleeve, sheath or tube that is made ofresilient or elastic material, such as silicone. The resilient sleevemay be positioned around the distal part, so that it is under torsionwhen the distal part is rotated away from the predetermined rotationalposition.

The spring can be a compression spring, or tension spring, or torsionspring. A helical torsion spring may be particularly suited for storingenergy when the distal part is rotated and for providing a biasing forceto return the distal part to its initial rotational orientation. Ahelical torsion spring may be positioned around the distal part, so thatthe helical torsion spring is under torsion when the distal part isrotated in the first direction away from an initial position.

The biasing element may therefore be considered to be a return springthat acts to return the distal part to an initial rotational orientationwhen the distal part is rotated away from the initial rotationalorientation in the first rotational direction.

The instrument may further comprise a stop element configured to preventrotation of the distal part in an opposite second rotational directionwhen the distal part contacts the stop element. Thus, the stop elementcan prevent the rotational bias from causing the distal part to rotatein the second rotational direction past a particular rotationalposition, for example an initial starting rotational orientation of thedistal part.

A predetermined rotational position towards which the distal part isbiased may be the same as an initial starting rotational position of thedistal part. Thus, the stop element may be configured to contact thedistal part when the distal part is at the predetermined rotationalposition.

Alternatively, in some embodiments it may be advantageous for the distalpart to experience the biasing force when it is in the initial startingrotational position, so that force is required to rotate the distal partaway from this position. In this case, the stop element may beconfigured to contact the distal part at the initial starting rotationalposition and this may be a different rotational position to apredetermined rotational position towards which the distal part isbiased.

The instrument may further comprise a tubular housing in which thecoaxial feed cable is received; and the distal part may be rotatablymounted at a distal end of the tubular housing. Thus, the distal partrotates relative to both the coaxial feed cable and the tubular housing.Rotatably mounted may mean that part of the distal part is received inthe distal end of the tubular housing and that the distal part is ableto rotate relative to the tubular housing. The tubular housing may bepart of or mounted on the flexible sleeve mentioned above. A seal may beformed adjacent to the distal end of the tubular housing to preventingress of fluid into the tubular housing.

The instrument may comprise an axial stop configured to prevent thedistal part from moving axially out of the end of the tubular housing.For example, the distal part may be rotatably received within a ringfixed in the distal end of the tubular housing and a protrusion may beprovided on the distal part that contacts an edge of the ring when thedistal part is moved axially towards the distal end of the tubularhousing, so that the distal part is prevented from being removed fromthe tubular housing.

The biasing element may be connected to the distal part and to thetubular housing. Thus, the biasing element may be deformed (e.g. madeunder compression, tension or torsion) when the distal part is rotatedwithin the tubular housing relative to the coaxial feed cable. Forexample, the biasing element may be connected at a first end thereof tothe distal part and at a second end thereof to the tubular housing.

The stop element may be connected to the tubular housing. Thus, thedistal part is prevented from rotating relative to the tubular housingin the second direction when the distal part contacts the stop element.

The distal part may comprise a second coaxial feed cable comprising asecond inner conductor (which may be solid or hollow), a second tubularouter conductor coaxial with the second inner conductor, and a seconddielectric material separating the second inner and outer conductors,the second coaxial feed cable being for conveying radiofrequency energyand/or microwave frequency energy to the instrument tip.

The second inner conductor may be electrically connected to the firstconductive element of the instrument tip and the second outer conductormay be electrically connected to the second conductive element of theinstrument tip. This electrical connection may be achieved through aconductor such as a conductive wire or conductive foil and a conductiveadhesive such as solder. Thus, radiofrequency energy and/or microwavefrequency energy can be delivered from the second coaxial feed cable tothe instrument tip for delivery to tissue.

The second coaxial feed cable may be connected to the coaxial feed cableby the rotatable connection. Thus, the instrument tip may be rotatablerelative to the coaxial feed cable by rotating the second coaxial feedcable relative to the coaxial feed cable. The second inner conductor maybe electrically connected to the inner conductor and the second outerconductor may be electrically connected to the outer conductor throughthe rotatable connection. Thus, radiofrequency energy and/or microwavefrequency energy can be delivered to the instrument tip from the coaxialfeed cable via the second coaxial feed cable.

A proximal end of the second inner conductor may protrude from aproximal end of the second coaxial feed cable; a distal end of the innerconductor may protrude from a distal end of the coaxial feed cable; andthe rotatable connection may comprise: a first conductive partcontacting the protruding proximal end of the second inner conductor andthe protruding distal end of the inner conductor and forming a rotatableelectrical connection therebetween; and a second conductive partcontacting a proximal end of the second outer conductor and a distal endof the outer conductor and forming a rotatable electrical connectionthere-between.

Thus, the second coaxial feed cable is able to rotate relative to thefirst coaxial feed cable while maintaining the electrical connectionsduring the rotation.

The second inner conductor and second outer conductor may be able torotate relative to the conductive parts, and/or the inner conductor andthe outer conductor may be able to rotate relative to the conductiveparts.

The second inner conductor and second outer conductor may be preventedfrom moving axially relative to the conductive parts, and/or the innerconductor and outer conductor may be prevented from moving axiallyrelative to the conductive parts, so as to maintain the rotatableelectrical connection.

The first conductive part and/or the second conductive part may be aconductive sleeve. In other words, the first conductive part and/or thesecond conductive part may be a conductive sheath or tube, for examplemade of metal. The conductive sleeve may surround the ends of theinner/outer conductors and contact the ends of the inner/outer conductorto form the electrical connection.

The conductive sleeve(s) may be an interference fit sleeve(s). This mayprevent axial movement of the inner/outer conductors relative to thesleeve(s).

The diameter of the protruding proximal end of the second innerconductor may be different from a main part of the second innerconductor; and the diameter of the protruding distal end of the innerconductor may be different from a main part of the inner conductor. Thediameter of the protruding parts may be selected to reduce an impedancemismatch between the coaxial cable or the second coaxial cable and therotation joint. Depending on the surrounding dielectric, the protrudingparts may be wider or narrower than their respective main parts. Forexample, the coaxial cable and/or the second coaxial cable may have acharacteristic impedance of 50Ω and the thickness of the protrudingdistal end of the inner conductor and/or the protruding proximal end ofthe second inner conductor may be increased or decreased so that theimpedance of the rotational joint is also substantially 50Ω.

The diameter of the protruding proximal end of the second innerconductor may be the same as the diameter of the protruding distal endof the inner conductor; and the diameter of the second outer conductormay be the same as the diameter of the outer conductor. This may reduceany impedance mismatch between the coaxial feed cable and the secondcoaxial feed cable.

The coaxial feed cable and the second coaxial feed cable may be the sametype of coaxial cable and may have the same impedance, for example 50Ω.

In some embodiments, the first conductive part may be fixed to theprotruding proximal end of the second inner conductor and to theprotruding distal end of the inner conductor; and the first conductivepart may be resiliently deformable by rotation of the second coaxialfeed cable relative to the coaxial feed cable. Thus, deformation of thefirst conductive part, i.e. torsion of the first conductive part, whenthe distal part is rotated relative to the coaxial feed cable may leadto a rotational biasing being applied to the distal part by the firstconductive part that acts to return the distal part to an initialrotational configuration in which the first conductive part is notdeformed.

In an alternative configuration the rotatable connection may comprise aflexible transmission line. Flexible means that the transmission linecan be deformed, for example twisted.

The flexible transmission line may comprise a flexible strip.

The flexible transmission line may be a flexible microstrip transmissionline, or a flexible stripline transmission line.

The transmission line may be a substantially planar transmission linewhen the distal part is in an initial rotational orientation.

The transmission line may be a printed transmission line.

The flexible transmission line may be elastically resilient. Thus, whenthe flexible transmission line is deformed by rotation of the distalpart, the flexible transmission line will provide a biasing force actingto return the distal part to an initial rotational orientation in whichthe transmission line is not deformed. The flexible transmission linemay therefore act as a return spring for returning the distal part to aninitial rotational orientation when the distal part is rotated away fromthe initial rotational orientation. Alternatively, a separate spring asdiscussed above may be provided to provide the rotational bias.

The flexible transmission line may have a first conductive pathelectrically connecting the inner conductor to the first conductiveelement and a second conductive path electrically connecting the outerconductor to the second conductive element.

The conductive paths may be electrically connected to the inner/outerconductor and/or to the first/second conductive elements using aconductive adhesive such as solder (possibly via another conductor, suchas a wire or foil).

The flexible transmission line may comprise a flexible microwavesubstrate.

The flexible transmission line may comprise a flexible microwavesubstrate having a first conductive path on a first surface thereof anda second conductive path on an opposite second surface thereof; thefirst conductive path may electrically connect the inner conductor tothe first conductive element; and the second conductive path mayelectrically connect the outer conductor to the second conductiveelement. Thus, the electrical connections are suitably maintained acrossthe flexible transmission line during rotation of the distal partrelative to the coaxial feed cable.

A distal end of the inner conductor may protrude from a distal end ofthe coaxial feed cable; and the first conductive path may be connectedto the protruding distal end of the coaxial feed cable. The connectionmay be achieved using a conductive adhesive such as solder.

The flexible microwave substrate may comprise a laminate structurecomprising two layers laminated together; and the two layers may bedelaminated at a distal end of the flexible microwave substrate to forma first layer having the first conductive path and a second layer havingthe second conductive path. This may be a suitable way of achievingelectrical connections to the first and second conductive elements.

The flexible microwave substrate may have a laminate structurecomprising two flexible microwave substrate layers laminated together;and the two flexible microwave substrate layers may be delaminated at adistal end of the flexible microwave substrate to form a first flexiblemicrowave substrate having the first conductive path and a secondflexible microwave substrate having the second conductive path.

The first conductive path may be connected to the first conductiveelement on a first surface of the instrument tip; and the secondconductive path may be connected to the second conductive element on anopposite second surface of the instrument tip.

The instrument may comprise an actuator element for rotating the distalpart relative to the coaxial feed cable; the actuator element may beconfigured to be moved axially along the instrument; and the distal partmay comprise an interface for converting axial movement of the actuatorelement into rotational movement of the distal part. Thus, the actuatordescribed above may comprise a proximal control portion, an actuatorelement and an interface. The proximal control portion is accessible bya user and imparts axial movement to the actuator element. The axialmovement is transformed by the interface into rotational movement of thedistal part. An advantage of this technique for rotating the distal partis that it is possible to precisely control the rotational orientationof the distal part.

The actuator element may be fed down the tubular housing. In otherwords, the actuator element may extend the whole length of the tubularhousing so that it can be operated by an operator at a proximal end ofthe tubular housing. Where the instrument is passed down an instrumentchannel of an endoscope, the actuator element may extend at least thewhole length of the instrument channel so that it can be operated by anoperator at a proximal end of the instrument channel.

The interface for converting axial movement of the actuator element intorotational movement of the distal part may comprise a path on the distalpart along which a part of actuator element travels when the actuatorelement is moved axially, thereby causing the distal part to rotate.

The path may be a raised path, a channel or a groove.

The path may be a helical path or a spiral path about a central axis ofthe distal part. In other words, the path may curve around at least partof a circumferential surface of the distal part and may extend along atleast part of an axial length of the distal part.

The path may be positioned on or around a circumferential surface of thedistal part.

The path may be a cam surface of the distal part that makes slidingcontact with a part of the actuator element when the actuator element ismoved axially, thereby causing the distal part to rotate. Part of acircumferential surface of the distal part may be cut away or omitted toprovide the cam surface. For example, a cam channel may be cut away oromitted from the surface of the distal part to provide the cam surface.Thus, when the actuator element is moved axially towards the distalpart, the distal part is caused to rotate by the part of the actuatorelement making sliding contact with the cam surface.

The cam surface may be an edge surface of a raised portion or wall thatextends outwardly away from a central axis of the distal part. Forexample, part of a circumferential surface of the distal part may be cutaway or omitted to leave the edge surface.

The instrument may be configured so that the cam surface makes slidingcontact with a distal end of the actuator element when the actuatorelement is moved axially, thereby causing the distal part to rotate.Thus, when the actuator element is moved axially towards the distalpart, the distal end of the actuator element contacts the cam surfaceand forces the distal part to rotate in the first rotational directionso that the distal end of the actuator element follows the cam surface.

The actuator element may be movable in the axial direction (towards thedistal part) so that a distal end of the actuator element passes adistal end of the path and protrudes from a distal end of the instrumenttip. As discussed below, this may be particularly advantageous where theactuator element is dual purpose, for example where it is a needle forinjecting fluid into tissue adjacent the instrument tip.

Once the distal end of the actuator element has passed a distal end ofthe path, the distal part may remain at its current rotational positionuntil the actuator element is moved axially along the instrument awayfrom the distal end so that the distal end of the actuator element onceagain contacts the path (or cam surface). When the distal end of theactuator element has passed the distal end of the path, the actuatorelement may be further displaced axially along the instrument towardsthe distal part without any further rotation of the instrument tip.

When the distal end of the actuator element passes the distal end of thepath (e.g. the cam surface) the actuator element may be positionedadjacent a side surface and/or adjacent a bottom surface of theinstrument tip.

While sufficient force is maintained on the actuator element, thebiasing is unable to force the distal part to return to its initialrotational orientation. However, when force is removed from the actuatorelement, the biasing may force the distal part to return to its initialrotational orientation. This may also force the actuator element toreturn to an original position, for example by forcing the actuatorelement to move axially away from the distal end.

The actuator element may be for rotating the distal part in a firstdirection relative to the coaxial feed cable when the actuator elementis moved in a first axial direction, and the actuator element may be forrotating the distal part in an opposite second direction relative to thecoaxial feed cable when the actuator element is moved in an oppositesecond axial direction. Thus, rotation of the instrument tip in eitherof the clockwise and anticlockwise direction can be achieved by movingthe actuator element in a forward or backward (first or second) axialdirection. In this case, it is not necessary to have any biasing meansacting to return the instrument tip to an original rotationalorientation, because the instrument tip can be returned to an initialrotational orientation by moving the actuator element axially to aninitial axial position.

The actuator element may comprise a helical shaped portion defining ahelical path, and the distal part may comprise a follower for causingthe distal part to rotatably follow the helical path when the actuatorelement is moved axially relative to the follower. Thus, as the actuatorelement is moved axially, the follower rotates to follow the helicalpath, causing the distal part and therefore the instrument tip torotate. An axial stop may be provided to prevent any axial movement ofthe follower, so that the follower is only able to rotate to follow thehelical path and cannot be axially displaced by the actuator element.

The follower may comprise a ring having a through-channel in which thehelical shaped portion of the actuator element is slidably received. Forexample, the through channel may be a slot or notch in the circumferenceof the ring. The shape of the through-channel may be substantially thesame as the cross-sectional shape of the helical portion of the actuatorelement, so that the follower closely follows the helical path as theactuator element is axially displaced.

The follower may be part of a tubular sleeve portion that is fixed tothe distal part. For example, the follower may be integral with, orfixed or connected to, the tubular sleeve portion, for example adjacenta proximal end of the sleeve portion. The tubular sleeve portion may befixed directly to the instrument tip, or to another part of the distalpart, such as a skirt portion of the distal part. The tubular sleeveportion rotates together with the distal part, so that rotation of thesleeve portion causes corresponding rotation of the distal part andtherefore the instrument tip.

The actuator element may comprise a rod, wire, cable, hollow tube orneedle.

The actuator element may comprise a needle for delivering/injectingfluid to biological tissue. Some known electrosurgical instruments usesuch needles to deliver/inject fluid to biological tissue and thereforeit may be advantageous to utilise this needle as the actuator elementrather than also providing a separate actuator element. The needle maytherefore be dual purpose. Thus, by axially moving the needle along theinstrument towards the instrument tip, the needle can be used to changeand control the orientation of the instrument tip. Where the distal partis biased, the orientation of the instrument tip can be controlledprecisely by moving the needle in either axial direction (forwards orbackwards) to achieve clockwise or anticlockwise rotation of theinstrument tip. Once the needle has been moved axially to a point whereit has passed the axial end of the path, the needle can be moved axiallyto inject fluid into tissue without affecting the rotational orientationof the instrument tip.

The instrument may also comprise a tubular needle housing for housingthe needle. For example, the tubular needle housing may be fed down thetubular housing and the needle may then be fed down the tubular needlehousing.

The instrument may comprise a guide part having a guide channel throughwhich the actuator element is fed. The guide part may prevent theactuator element from being moved sideways by the rotational bias thatis applied to the distal part. The guide part may constrain the actuatorelement to only be able to move in an axial direction. For example,where the actuator element is the needle, the needle may be fed throughthe guide channel directly, or the tubular needle housing containing theneedle may be fed through the guide channel.

The guide part may be fixed to the tubular housing. Thus, the actuatorelement may be constrained to only be able to move in an axial directionrelative to the tubular housing. This will prevent the actuator elementfrom moving sideways when it is used to rotate the distal part.

The instrument tip may comprise a planar body made of a dielectricmaterial separating the first conductive element on a first surfacethereof from the second conductive element on a second surface thereof,the second surface facing in the opposite direction to the firstsurface.

The distal part may further comprise a protective hull mounted to coverthe underside of the planar body. The protective hull may have asmoothly contoured convex under surface facing away from the planarbody; the planar body may have a tapering distal edge; and the undersideof the planar body may extend beyond the protective hull at the taperingdistal edge.

According to a second aspect of the present invention there is providedelectrosurgical instrument for applying radiofrequency energy and/ormicrowave frequency energy to biological tissue, the instrumentcomprising: an instrument tip for applying radiofrequency energy and/ormicrowave frequency energy to biological tissue; a coaxial feed cablefor conveying radiofrequency energy and/or microwave frequency energy tothe instrument tip; a housing surrounding the coaxial feed cable; and aplurality of bearings positioned between the coaxial feed cable and thehousing for enabling rotation of the coaxial feed cable relative to thehousing.

Thus, rotation of the instrument tip can be achieved by rotating thewhole coaxial feed cable within the housing, which is possible becauseof the plurality of bearings.

The electrosurgical instrument according to the second aspect of thepresent invention may have any one, or, to the extent they arecompatible, any combination of the following optional features.

The electrosurgical instrument may be configured for passing through aninstrument channel of an endoscope. Thus, rotation of the instrument tipat the distal end of the instrument channel can be achieved by rotatingthe coaxial feed cable at the proximal end of the instrument channel.

The bearings may be any device, component or part that reduce frictionbetween the coaxial feed cable and the housing sufficiently to enablecontrollable rotation of the coaxial feed cable relative to the housing.For example, the bearings may be rolling element bearings that includerolling elements such as ball bearings, or brush bearings.

There may be only two bearings, one at or close to the distal end of thehousing and one at or close to the proximal end of the housing.Alternatively, there may be more than two bearings. Providing additionalbearings may help to ensure smooth rotation of the instrument tip,particularly when the housing is bent, by reducing the contact betweenthe coaxial feed cable and the housing.

Other features of the electrosurgical instrument according to the secondaspect of the present invention may be the same as the features of thefirst aspect of the present invention set out above, where compatible.

The electrosurgical instrument according to the first or second aspectof the present invention may have any one, or, where compatible, anycombination of the following optional features.

A electrical length of the rotatable section, i.e. the section from thedistal end of the coaxial feed cable to the point at which energy isdelivered into tissue may be substantially equal to a multiple of

$\frac{\lambda}{2},$

where λ is the wavelength of microwave frequency energy having apredetermined frequency in the instrument tip. The predeterminedfrequency may be 5.8 GHz. This arrangement effectively makes thetransmission line formed by the rotatable section transparent orinvisible in terms of mismatch if the insertion loss is negligible. Thisarrangement may be used as a way of locating the rotatable jointproximally from the instrument tip. For example, the rotatable joint maybe position up to 8 cm back from the instrument tip. In this manner itis kept out of the way of the distal end of the scope, where there isoften maximum distortion in the instrument channel through manipulationof the scope device and where control lines may be connected.

In another embodiment, a half-wavelength rotation section may be located6 cm or 8 cm or 10 cm back from the distal end of the instrument andthen a quarter wavelength transformer may be disposed at (or integratedinto) the distal end of the instrument (e.g. instrument tip or endeffecter) to match the impedance of the rotation section to theimpedance of the biological tissue at the predetermined frequency.

In another embodiment, a half-wavelength rotation section may disposedat (or integrated into) the distal end of the instrument (e.g.instrument tip or end effecter). This arrangement assumes that theimpedance of the biological tissue at the predetermined frequency is thesame as the characteristic impedance of the coaxial feed cable. Thisassumption is reasonable for the delivery of energy at 5.8 GHz intoblood using a 50 n cable.

The distal part may comprise an impedance transformer that substantiallymatches a characteristic impedance of the coaxial transmission line to acharacteristic impedance of a tissue load in contact with the instrumenttip at the predetermined frequency.

A length of the impedance transformer may be substantially equal to

${\left( {{2n} + 1} \right)\frac{\lambda}{4}},$

where n is an integer number greater than or equal to zero and λ is thewavelength of the microwave frequency energy in the impedancetransformer at the predetermined frequency.

The distal part may further comprise a section of coaxial transmissionline between the impedance transformer and a proximal end of theinstrument tip.

Alternatively, a characteristic impedance of the instrument tip may besubstantially equal to a characteristic impedance of the coaxial feedcable; and the distal part may comprise an impedance matching sectionfor matching the characteristic impedance of the coaxial feed cable tothe impedance of a tissue load in contact with the instrument tip at thepredetermined frequency of microwave frequency energy, wherein theimpedance matching section comprises: a length of coaxial transmissionline connected to a proximal end of the instrument tip; and a shortcircuited stub.

The aspects of the invention discussed above present a rotatable portionfor a distal part of an electrosurgical instrument. In some embodimentsit may be desirable to provide a plurality of rotatable joints along thelength of the coaxial feed cable.

BRIEF DESCRIPTION OF THE DRAWINGS

Embodiments of the present invention will now be discussed, by way ofexample only, with reference to the accompanying Figures, in which:

FIGS. 1A to 1D illustrate a method of manufacturing a rotatableconnection used in an embodiment of the present invention;

FIGS. 2A and 2B illustrate a further rotatable connection used in afurther embodiment of the present invention;

FIGS. 3A and 3B show various configurations of a working model of anelectrosurgical instrument according to an embodiment of the presentinvention;

FIGS. 4 and 5 show various configurations of a working model of anelectrosurgical instrument according to an embodiment of the presentinvention;

FIG. 6 is a schematic illustration of an instrument tip according to anembodiment of the present invention;

FIG. 7 is a schematic illustration of an instrument tip according to afurther embodiment of the present invention;

FIG. 8 is a schematic illustration of an electrosurgical instrumentaccording to an embodiment of the present invention;

FIG. 9 is a sketch of an electrosurgical instrument according to anembodiment of the present invention;

FIG. 10 is a schematic illustration of an electrosurgical instrumentaccording to an embodiment of the present invention;

FIG. 11 is an enlarged schematic illustration of the portion of theelectrosurgical instrument of FIG. 10 shown with the circle in FIG. 10;

FIG. 12 is a schematic illustration of an electrosurgical instrumentaccording to a further embodiment of the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS AND FURTHER OPTIONALFEATURES OF THE INVENTION

FIGS. 1A to 1D illustrate a method of manufacturing a rotatableconnection used in an embodiment of the present invention.

As shown in FIGS. 1A to 1D, a rotatable connection is being formedbetween a coaxial feed cable 1 and a second coaxial feed cable 3. Eachof the coaxial feed cables 1, 3 comprises a solid cylindrical innerconductor, a tubular outer conductor that is coaxial with and surroundsthe inner conductor, and a dielectric material separating the inner andouter conductors.

In the embodiment of FIG. 1, the coaxial feed cable 1 and the secondcoaxial feed cable 3 are the same type of coaxial cable, specificallySucoform® 047 coaxial cable. In this type of coaxial cable, the innerconductor has an outer diameter of 0.31 mm, the dielectric materiallayer has an outer diameter of 0.94 mm, and the outer conductor has anouter diameter of 1.2 mm. This type of coaxial cable has acharacteristic impedance of 50Ω. The centre conductor is a silver platedcopper wire, the dielectric is PTFE and the outer conductor is tinsoaked copper braid.

Of course, in other embodiments another type of coaxial cable may beused, and/or the coaxial cable and the second coaxial cable may bedifferent types of coaxial cable with different dimensions and/orcharacteristic impedances.

As shown in FIG. 1B, a section of the dielectric material and outerconductor of the coaxial feed cable 1 has been omitted or removed toleave a protruding distal end 5 of the inner conductor that protrudesfrom the distal end of the coaxial feed cable 1. Similarly, a section ofthe dielectric material and outer conductor of the second coaxial feedcable 3 has been omitted or removed to leave a protruding proximal end 7of the inner conductor of the second coaxial feed cable (the secondinner conductor) that protrudes from the proximal end of the coaxialfeed cable 1.

As shown in FIGS. 1A and 1C, a rotatable electrical connection is formedbetween the inner conductors of the coaxial feed cable 1 and secondcoaxial feed cable 3 by providing a first conductive metal sleeve 9 overthe protruding ends 5, 7 of the inner conductors. The first conductivemetal sleeve 9 is a metal tube with a diameter chosen so that theprotruding ends 5, 7 of the inner conductors are rotatably received inthe metal tube and contact the metal tube to form an electricalconnection therebetween. In this embodiment, the first conductive metalsleeve 9 is an interference fit to the protruding ends 5, 7 of the innerconductors.

In this embodiment the first conductive metal sleeve 9 has an outerdiameter of 0.59 mm and a length of 2.5 mm. Of course, in otherembodiments these dimensions may be different.

Thus, the inner conductor and the second inner conductor are able torotate relative to each other while an electrical connection ismaintained there-between because of the rotatable connection provided bythe first conductive metal sleeve 9.

As shown in FIGS. 1A, 1C and 1D, a rotatable electrical connection isformed between the outer conductor 11 of the coaxial feed cable 1 andthe outer conductor 13 of the second coaxial feed cable 3 (the secondouter conductor) by providing a second conductive metal sleeve 15 overthe ends of the outer conductors 11, 13. As shown in FIG. 1C, the secondconductive metal sleeve 15 can be positioned over the ends of the outerconductors 11, 13 by sliding it along one of the coaxial feed cables 1,3 until it is positioned over the ends of the outer conductors 11, 13.

The second conductive metal sleeve 15 is a metal tube with a diameterchosen so that the ends of the outer conductors 11, 13 are rotatablyreceived in the metal tube and contact the metal tube to form anelectrical connection therebetween. In this embodiment, the secondconductive metal sleeve 15 is an interference fit to the ends of theouter conductors 11, 13.

In this embodiment the second conductive metal sleeve 15 has an innerdiameter of 1.15 mm. Of course, in other embodiments the diameter may bedifferent.

Thus, the outer conductors 11, 13 of the coaxial feed cable 1 and thesecond coaxial feed cable 3 are able to rotate relative to each otherwhile an electrical connection is maintained there-between because ofthe rotatable connection provided by the second conductive metal sleeve15.

Thus, the combination of the first and second conductive metal sleeves11, 13 provides a rotatable connection between the coaxial feed cable 1and the second coaxial feed cable 3 that allows the second coaxial feedcable 3 to be rotated relative to the coaxial feed cable 1, whilemaintaining an electrical connection between the coaxial feed cable 1and the second coaxial feed cable 3.

Radiofrequency energy and/or microwave frequency energy can betransmitted from the coaxial feed cable 1 to the second coaxial feedcable 3 through the rotatable connection because of the rotatableelectrical connections provided by the first and second conductive metalsleeves 9, 15.

The first and second conductive metal sleeves 9, 15 form a coaxialtransmission line for conveying the radiofrequency energy and/ormicrowave energy with air as the dielectric material. In otherembodiments a dielectric filler material may be provided between thefirst and second conductive metal sleeves 9, 15

In an embodiment of the present invention, the second coaxial feed cable3 may be connected to an instrument tip and may convey radiofrequencyenergy and/or microwave frequency energy from the coaxial feed cable 1to the instrument tip. For example, the instrument tip may have a firstconductive element electrically connected to the second inner conductorand a second conductive element electrically connected to the secondouter conductor. Thus, the instrument tip is rotatable relative to thecoaxial feed cable 1 by the rotatable connection. The electricalconnections may be achieved with electrical conductors such asconductive wires or sheets that are connected to the conductive elementsof the instrument tip and to the conductors by conductive adhesive, suchas solder.

The coaxial feed cable 1 may have a connector at a proximal end thereoffor connecting the coaxial feed cable 1 to an electrosurgical generatorfor supplying the radiofrequency energy and/or microwave frequencyenergy. For example, the connector may be a conventional coaxial cableend connector.

Having air as the dielectric material between the first and secondconductive metal sleeves 9, 15 as in FIG. 1 will increase thecharacteristic impedance of the rotational joint relative to theimpedance(s) of the coaxial feed cables 1, 3. The impedance mismatchbetween the coaxial feed cables 1, 3 and the rotational joint will leadto reflection of some of the radiofrequency energy and/or microwavefrequency energy. Therefore, in one embodiment the protruding ends 5, 7of the inner conductors may have an increased diameter, and the firstconductive metal sleeve 9 may have a correspondingly larger internaldiameter. Thus, the impedance of the rotational joint will be decreased,so that it is closer to the impedance of the coaxial feed cables 1, 4.Ideally, the impedance of the rotational joint would be the same as theimpedance of the coaxial feed cables, for example 50 Ohms.

The electrical properties of the rotational joint illustrated in FIGS.1A to 1D are now described.

The characteristic impedance Z₀ of a coaxial transmission line isapproximately given by equation (1).

$\begin{matrix}{Z_{0} \cong {138\sqrt{\frac{\mu_{r}}{ɛ_{r}}}\log_{10}\frac{b}{a}}} & (1)\end{matrix}$

Where μ_(r) is the relative permeability of the dielectric material,ε_(r) is the relative permittivity of the dielectric material, b is theinner diameter of the outer conductor and a is the outer diameter of theinner conductor. The ratio

$\frac{b}{a}$

may be obtained using the respective radii of the outer conductor andinner conductor.

The attenuation of the radiofrequency energy and/or microwave frequencyenergy because of the rotational joint is given in equation (2).

α_(T)=α_(c)+α_(d)  (2)

Where α_(T) is the total attenuation of the rotational joint, ac is theattenuation due to the first and second conductive metal sleeves 9, 15in the rotational joint and ad is the attenuation due to the dielectric(air in FIG. 1) in the rotational joint.

The attenuation due to the conductor is given in equation (3).

$\begin{matrix}{\alpha_{c} = {1{3.6}\frac{\delta_{s}\sqrt{ɛ_{r}}\left( {1 + \frac{b}{a}} \right)}{\lambda_{0} \times b \times \ln\frac{b}{a}}\mspace{14mu}{dB}\text{/}m}} & (3)\end{matrix}$

Where δ_(S) is the skin depth of the radiofrequency energy and/ormicrowave frequency energy within the first and second conductive metalsleeves 9, 15, ε_(r) is the relative permittivity, λ₀ is the free spacewavelength, b is the inner diameter of the outer conductor and a is theouter diameter of the inner conductor.

The attenuation due to the dielectric is given in equation (4)

$\begin{matrix}{\alpha_{d} = {2{7.3}\frac{\sqrt{ɛ_{r}}}{\lambda_{0}}\tan\;\delta\mspace{14mu}{dB}\text{/}m}} & (4)\end{matrix}$

In the embodiment illustrated in FIG. 1, the first conductive metalsleeve 9 has an outer diameter of 0.59 mm and a length of 2.5 mm. Thesecond conductive metal sleeve 15 has an inner diameter of 1.15 mm.

With air as the dielectric material between the first and secondconductive metal sleeves 9, 15 the impedance and attenuation due to theconductors of the rotational joint are given in equations (5) and (6).

$\begin{matrix}{Z_{0} = {{138\sqrt{\frac{1}{1.00059}}\log\frac{0.575}{0.295}} = {3{9.8}8\mspace{14mu}\Omega}}} & (5) \\{\alpha_{c} = {{1{3.6}\frac{\left( {{0.8}6 \times 10^{- 6}} \right)\sqrt{1}\left( {1 + \frac{0.575}{0.295}} \right)}{0.0517 \times 0.575 \times {Ln}\;\frac{{0.5}75}{{0.2}95}}} = {{1.7}38\mspace{14mu}{dB}\text{/}m}}} & (6)\end{matrix}$

Assuming that the air filled rotational joint has tan δ=0, theattenuation due to the dielectric is given in equation (7).

$\begin{matrix}{\alpha_{d} = {{2{7.3}\frac{\sqrt{1.00059}}{0.0517} \times 0} = 0}} & (7)\end{matrix}$

Relating these equations to the specific length of the first conductivemetal sleeve 9 of 2.5 mm in this particular embodiment leads to equation(8).

$\begin{matrix}{{\alpha = {{\alpha_{c} + \alpha_{d}} = {{1.7}38\mspace{14mu}{dB}\text{/}m}}}{\alpha = {{\frac{{1.7}38\mspace{14mu}{dB}}{m} \times {0.0}025\mspace{14mu} m} = {0.004346\mspace{14mu}{dB}}}}} & (8)\end{matrix}$

Equation (8) gives the associated loss within the 2.5 mm length rotatingsleeve section. This calculation does not take into account any smallimpedance mismatch between the characteristic line impedance and therotating joint. The slight mismatch will increase insertion loss due toincreased reflection, but in testing it has been found that thisincrease is negligible.

A layer of insulation may be provided between the first and secondconductive metal sleeves 9, 15 to prevent electrical breakdown of theair between the metal sleeves 9, 15 during radiofrequency energyoperation of the instrument. For example, the insulation may be Kaptontape or PTFE.

In one embodiment, the first conductive metal sleeve 9 may be fixed tothe protruding ends 5, 7 of the inner conductors. The first conductivemetal sleeve 9 may be made of a resiliently deformable material, so thatthe first conductive metal sleeve 9 is resiliently deformed (e.g.twisted under torsion) when the second coaxial feed cable 3 is rotatedrelative to the coaxial feed cable 1. Thus, the first conductive metalsleeve 9 may provide a rotational biasing force on the second coaxialfeed cable 3 causing it to return to an initial rotational orientationin which the first conductive metal sleeve 9 is not deformed. Thus, thefirst conductive metal sleeve 9 may act as a return spring.

Of course, in other embodiments of the present invention a differenttype of rotatable connection may be provided. Many different types ofsuch rotatable connection are possible. Specific methods for controllingthe rotation of an electrosurgical instrument at the distal end of thearrangements illustrated in FIGS. 1A to 1D are discussed below.

FIGS. 2A and 2B illustrate a further rotatable connection used in afurther embodiment of the present invention.

As illustrated in FIGS. 2A and 2B, in this embodiment the coaxial feedcable 1 is connected to an electrosurgical instrument tip 17 by aflexible transmission line 19. Flexible means that the transmission linecan be deformed, for example twisted or bent, without being broken orpermanently damaged. For example, it can be twisted under torsion.

The flexible transmission line 19 comprises a flexible microwavesubstrate 21. For example, the flexible microwave substrate 21 might beRFlex microwave substrate from Rogers Corporation.

The flexible transmission line 19 electrically connects the innerconductor 22 of the coaxial feed cable 1 to a first conductive element23 on an underside of the instrument tip 17 and also electricallyconnects the outer conductor 25 to a second conductive element 27 on an(opposite) upper side of the instrument tip 17. Thus, the flexibletransmission line 19 is configured to convey radiofrequency energyand/or microwave frequency energy from the coaxial feed cable 1 to thefirst and second conductive elements 23, 27 of the instrument tip 17,for delivery into tissue in contact with the instrument tip 17.

The electrical connection between the inner conductor 22 and the firstconductive element 23 is achieved by a first conductive path formedalong the length of the flexible transmission line 19 that iselectrically connected to the inner conductor 21 and to the firstconductive element 23 by a conductive adhesive such as solder 29. Thefirst conductive path may be formed of metal, and may be printed on asurface of the flexible microwave substrate 21, for example on anunderside of the flexible microwave substrate 21.

Similarly, the electrical connection between the outer conductor 25 andthe second conductive element 27 is achieved by a second conductive path31 formed along the length of the flexible transmission line 19 that iselectrically connected to the outer conductor 25 and to the secondconductive element 27 by a conductive adhesive such as solder 29. Thesecond conductive path 31 may be formed of metal, and may be printed onthe opposite surface of the flexible microwave substrate 21, for exampleon an upper side of the flexible microwave substrate.

In this embodiment, the instrument tip 17 comprises a planar body madeof a dielectric material 33 separating the first conductive element 23on a first surface thereof from the second conductive element 27 on asecond surface thereof, the second surface facing in the oppositedirection to the first surface.

The first and second conductive paths may be made of copper. The firstand second conductive paths may be printed on the flexible transmissionline.

In the embodiment shown in FIGS. 2A and 2B, the flexible transmissionline 19 is split into two parts 19 a, 19 b adjacent to the instrumenttip 17. The first part 19 a has the second conductive path 31 on anupper surface thereof and the second part 19 b has the first conductivepath on a bottom surface thereof. Splitting of the flexible transmissionline 19 may be achieved by using a laminated flexible transmission line19 that comprises two layers of material laminated together, anddelaminating the two layers of material adjacent to the instrument tip17 to split the flexible transmission line 19 into two parts asillustrated in FIG. 2.

However, in other embodiments, the flexible transmission line 19 doesnot divide in this manner. Instead additional connector portions may beprovided to connect the conductive paths on the flexible substrate totheir respective terminals on the instrument tip.

In this embodiment the flexible transmission line 19 is substantiallyplanar and substantially flat when in an initial (non-twisted)configuration. The flexible transmission line is in the form of aflexible (twistable) strip.

Since the flexible transmission line 19 is flexible, if the instrumenttip 17 is rotated relative to the coaxial feed cable 1, the flexibletransmission line 19 allows the rotation by deforming. Specifically, theflexible transmission line 19 will be under torsion and will twist whenthe instrument tip 17 is rotated relative to the coaxial feed cable 1.Thus, the flexible transmission line 19 constitutes a rotatableconnection between the coaxial feed cable 1 and the instrument tip 17that allows rotation of the instrument tip 17 relative to the coaxialfeed cable 1, while maintaining the electrical connections between theinner/outer conductors 22, 25 of the coaxial feed cable 1 and thefirst/second conductive elements 23, 27 of the instrument tip 17.Radiofrequency energy and/or microwave frequency energy can thus beconveyed from the coaxial feed cable 1 to the instrument tip 17 via theflexible transmission line 19 during rotation of the instrument tip 17relative to the coaxial feed cable.

The flexible transmission line 19 may be elastically resilient. In otherwords, when the flexible transmission line is deformed by twisting ofthe flexible transmission line 19, it may provide a biasing force toreturn the flexible transmission line to an original (e.g. flat)orientation. Thus, the flexible transmission line 19 may also functionas a return spring for returning the instrument tip 17 to an initialrotational position in which the transmission line is substantially flatwhen the instrument tip 17 is rotated away from the initial position.

The flexible transmission line 19 may have a coating, covering, or otherseal to prevent liquid from coming into contact with the electricalconnections or paths. For example, the flexible transmission line 19 maycomprise a layer or coating of insulating material, such as a rubbermaterial or polymer, on one or more surface thereof, to prevent liquidfrom coming into contact with an electrical connection or path of theflexible transmission line 19. Alternatively, seals may be providedadjacent to each axial end of the flexible transmission line 19 toprevent liquid from coming into contact with the flexible transmissionline 19.

In some embodiments, the flexible transmission line may be a flexiblemicrostrip. In such embodiments, the flexible transmission linecomprises a planar conducting strip separated from a ground plane by asubstrate dielectric layer. The microstrip may be fabricated usingprinted circuit board technology. The ground plane and planar conductingstrip may each be electrically connected to a respective one of thefirst and second conductive elements of the instrument tip. In suchembodiments, the planar conducting strip and ground plane may beprevented from coming into contact with liquid by a coating, covering orother seal as described above. As described above, the substratedielectric layer may be a laminate structure which can be split adjacentto the instrument tip to allow electrical connection of the flexiblemicrostrip to conductive elements on opposite surfaces of the instrumenttip.

In alternative embodiments the flexible transmission line may be aflexible stripline. In such embodiments, the flexible transmission linecomprises a central conductor formed within a substrate dielectric layerthat is sandwiched between ground planes on opposite sides of thesubstrate dielectric layer. Such an arrangement has an advantage thatthe central conductor is prevented from coming into contact with liquidbecause it is surrounded by the dielectric layer, so it may not benecessary to provide any further barriers to prevent liquid coming intocontact with the flexible transmission line. With this structure, whenforming the electrical connection to the instrument tip, the groundplanes can be terminated a predetermined distance before the distal endof the flexible transmission line.

In the embodiment illustrated in FIGS. 2A and 2B, the flexibletransmission line 19 directly connects the coaxial feed cable 1 to theinstrument tip 17. However, this is not essential. For example, theflexible transmission line 19 may be set back from the instrument tipand a further coaxial transmission line may be provided between theflexible transmission line 19 and the instrument tip 17, to space theflexible transmission line 19 from the other parts at the distal end ofthe cable arrangement. However, it is advantageous to have the flexibletransmission line 19 close to the instrument tip 17 to enable suitablecontrol of the rotation of the instrument tip 17. Furthermore, inembodiments where the instrument tip 17 has a planar structure, forexample as shown in FIGS. 2A and 2B, it is advantageous for the flexibletransmission line 19 to directly connect the coaxial feed cable 1 to theinstrument tip 17, because the flexible transmission line 19 convertsthe round/cylindrical structure of the coaxial feed cable 1 to theflat/planar structure of the instrument tip 17.

Of course, in other embodiments the flexible transmission line may bedifferent to that shown in FIGS. 2A and 2B or described above. Theimportant feature is that the flexible transmission line provides thenecessary electrical connections and allows rotation of the instrumenttip relative to the coaxial feed cable.

In other embodiments a different type of rotatable connection may beprovided between the coaxial feed cable 1 and the instrument tip tothose illustrated in FIGS. 1A to 2B. The important feature is that therotatable connection provides the necessary electrical connections andallows rotation of the instrument tip relative to the coaxial feedcable.

Mechanisms for causing rotation of an instrument tip relative to acoaxial feed cable and mechanisms for providing a rotational bias to theinstrument tip will now be discussed. Although the rotation and biasingmechanisms are combined together in the embodiment described below,other embodiments of the present invention may have only one of thesespecific mechanisms, e.g. just the rotation mechanism or just thebiasing mechanism.

FIGS. 3A to 5 show various configurations of a model of anelectrosurgical instrument 35 according to an embodiment of the presentinvention. As shown in FIGS. 3A to 5, the instrument 35 comprises aninstrument tip 37 and a coaxial feed cable 39 that is fixed to theinstrument tip 37. In practice, the instrument tip 37 will comprisefirst and second conductive elements for delivering radiofrequencyenergy and/or microwave frequency energy into biological tissue incontact with the instrument tip 37. For example, the instrument tip mayhave a structure similar to that of the instrument tip illustrated inFIG. 2A.

In practice, the coaxial feed cable 39 is fixed to the instrument tip 37by an inner conductor of the coaxial feed cable 39 being fixed byconductive adhesive such as solder to a first of the conductive elementsof the instrument tip 37, and by an outer conductor of the coaxial feedcable 39 being fixed by conductive adhesive such as solder to a secondof the conductive elements (possibly via additional conductors such aswire or foil).

Thus, the instrument tip 37 cannot rotate relative to the coaxial feedcable 39.

The coaxial feed cable 39 (or at least some of the coaxial feed cable39) is received within a tubular housing 41. For example, the tubularhousing 41 may be a flexible plastic or polymer tube. The coaxial feedcable 39 may be fed along the tubular housing 41. The coaxial feed cable39 is able to rotate relative to the tubular housing 41. In other words,the coaxial feed cable 39 is not fixed relative to the tubular housing41. In FIG. 5 the tubular housing 41 is shown as being opaque, which itis likely to be in practice.

The instrument tip 37 is rotatably mounted at a distal end of thetubular housing 41. In other words, part of the instrument tip 37 isreceived in the distal end of the tubular housing 41 and can rotaterelative to the tubular housing 41. This may be achieved by theinstrument tip 37 having a shaft or a shank portion at the proximal endthereof that is shaped to be received in the distal end of the tubularhousing so that is can rotate therein. Alternatively, a tubular part maybe fixed around an outside of part of a shaft or shank portion of theinstrument tip, wherein the tubular part is received within the distalend of the tubular housing 41 and can rotate relative to the tubularhousing 41.

Thus, both the instrument tip 37 and the coaxial feed cable 39 form adistal part of the instrument 35 that is able to rotate relative to thetubular housing 41.

A stop part may be provided on the instrument tip 37, or in the distalend of the tubular housing 41, to prevent the instrument tip from movingaxially out of the distal end of the tubular housing. A seal may also beprovided on a part of the instrument tip 37, to prevent the ingress offluid into the tubular housing 41. For example, a seal may be providedon or around a part of a shaft or shank portion of the instrument tip 37that is received in the tubular housing 41,

As shown in FIGS. 3A to 4, a spring 43 is also provided in the tubularhousing 41. The spring 43 is a helical torsion spring that is positionedaround the outside of the coaxial feed cable 39.

A first end of the spring 43 is fixed to the tubular housing 41. In thisembodiment, the first end of the spring 43 is fixed to the tubularhousing 41 by being fixed to a ring part 45 that is fixed to an internalsurface of the tubular housing 41. A second end of the spring 43 isfixed to the distal part of the instrument 35. Specifically, the secondend of the spring is connected to a skirt portion 47 that extendsaxially from the instrument tip 37 towards the proximal end of theinstrument 35. The skirt portion 47 is integral with the instrument tip37 and rotates together with the instrument tip 37.

Thus, if the distal part of the instrument 35 comprising the instrumenttip 37, skirt portion 47 and coaxial feed cable 39 is rotated within thetubular housing 41 towards the right in FIG. 3A, the helical torsionspring 43 is twisted because its second end rotates with the distal partwhereas its first end is fixed to the tubular housing 41. Thus,mechanical energy is stored in the helical torsion spring 43. Thisstored mechanical energy causes the helical torsion spring 43 to exert arotational biasing force on the distal part that biases the distal partto rotate in the opposite direction, i.e. towards the left in FIG. 3A.

Thus, the helical torsion spring 43 functions as a reset spring thatprovides a force for resetting the distal part to an initial rotationalposition/orientation when the distal part is rotated away from thatrotational position/orientation.

In practice, the coaxial feed cable 39 will be connected to a furthercoaxial feed cable by a rotatable connection such as that illustrated inFIGS. 1A to 1D and described above, so that radiofrequency energy and/ormicrowave frequency energy can be conveyed to the coaxial feed cable 39(and therefore to the instrument tip 37) from the further coaxial feedcable and so that the coaxial feed cable 39 (and therefore the distalpart of the instrument 35) can rotate relative to the further coaxialfeed cable. In practice the further coaxial feed cable will be connectedto an electrosurgical generator for generating and supplying theradiofrequency energy and/or microwave frequency energy.

The instrument comprises a stop element configured to prevent rotationof the distal part in a particular rotational direction (to the left inFIG. 3A) when the distal part contacts the stop element. Thus, the stopelement can prevent the rotational bias from causing the distal part torotate in the particular rotational direction beyond a particularrotational position, for example an initial starting rotationalorientation of the distal part. The stop element and/or the spring 43may be configured so that the spring 43 applies a bias force to thedistal part when the distal part is in an initial position in contactwith the stop element. Thus, in order to rotate the distal part awayfrom the initial position force must be applied to overcome therotational bias.

Of course, a similar biasing method to that illustrated in FIG. 3A maybe used with other types of rotatable connection between the instrumenttip and the main coaxial feed cable (the coaxial feed cable that isnormally connected to an electrosurgical generator). For example, thecoaxial feed cable 39 in FIG. 3A could be replaced with a flexibletransmission line, for example as illustrated in FIGS. 2A and 2B anddescribed above, which is connected (preferably fixed) to the maincoaxial feed cable. The helical torsion spring 43 could then bepositioned around the flexible transmission line, or around another partof the distal part of the instrument 35, so that the same biasing effectis achieved when the instrument tip is rotated and the flexibletransmission line is twisted.

Alternatively, in other embodiments the biasing force may be provided bypart of the rotatable connection, as discussed above in relation toFIGS. 1A to 2B (for example by the flexible transmission line beingelastically resilient), and therefore the spring 43 in FIG. 3A may beomitted in these embodiments (this configuration is discussed in moredetail below in reference to FIG. 9).

The biasing force may be provided by another resilient element, such asa resilient sleeve, instead of by the spring 43.

Of course, in yet further embodiments there may be no need or desire fora rotational bias force on the instrument tip at all, and therefore thespring 43 in FIG. 3A may also be omitted in these embodiments. Such anembodiment is discussed below in relation to FIGS. 10 and 11.

A mechanism for rotating the instrument tip 37 will now be described.

In FIG. 3A, the instrument tip 37 is rotated using an actuator element49 in the form of a rod 49 that is fed down the tubular housing 41 andthat can be moved axially along the tubular housing 41 by an operator ofthe instrument 35. As discussed below, in some embodiments the rod 49may be a needle of the instrument for injecting fluid such as salineinto tissue adjacent the instrument tip.

As best seen in FIG. 3B, the instrument comprises a guide part 51 havinga guide channel 53 through which the actuator element 49 is fed. Theguide part 51 prevents the actuator element 49 from being moved sidewaysby the rotational bias that is applied to the distal part. Specifically,the guide part 51 constrains movement of the actuator element 49 so thatit can only move in the axial direction relative to the guide part 51.In this embodiment, the guide part 51 is a ring fixed to an internalsurface of the tubular housing 41 and surrounding the coaxial feed cable39. As shown in FIG. 3B, the ring has an axial guide channel 53 throughwhich the actuator element 49 is fed. Thus, the actuator element 49 isable to move axially relative to the ring but cannot move sidewaysbecause it is constrained to remain within the guide channel 53.

The axial guide channel 53 may comprise a segment of the ring that isomitted or cut away (so that is it not a complete ring) or a bore orchannel formed in, or through, the ring.

The rotatable distal part of the instrument 35 comprises an interfacefor converting axial movement of the actuator element 49 into rotationalmovement of the distal part.

In this embodiment, the interface comprises a cam surface of theinstrument tip. The cam surface is a raised helical edge 55 (or spiraledge) that extends in a helical (or spiral) manner around at least partof an outer surface of the instrument tip 37 and along at least part ofthe length of the instrument tip. The helical edge 55 may be formed bycutting away or omitting a suitably shaped portion of the outer surfaceof the instrument tip 37 (e.g. to form a cam channel).

The raised helical edge 55 is configured so that it is contacted by adistal end 56 of the actuator element 49 as the actuator element 49 ismoved axially along the instrument 35 towards the instrument tip 37, sothat the distal end of the actuator element 49 slides along the raisedhelical edge 55 and forces the instrument tip 37 to rotate.

In some embodiments the helical edge 55 may have a curved surface, likea channel or groove, to better cooperate (e.g. receive or engage) withthe distal end of the actuator element 49.

As the actuator element 49 is moved axially along the instrument 35, thedistal end 56 of the actuator element 49 contacts the raised helicaledge 55 on the instrument tip 37. The actuator element 49 is only freeto move in the axial direction because of the guide part 51. Theinstrument tip 37 is prevented from moving axially, for example by afurther stop part that prevents axial movement of the instrument tip 37,but is free to rotate within the tubular housing 41. Thus, the action ofthe distal end of the actuator element 49 contacting and applying forceto the raised helical edge 55 causes the raised helical edge 55 to bedisplaced sideways, so that the actuator element 49 continues to moveaxially and to slide along the raised helical edge 55 so that theinstrument tip 37 starts to rotate. In FIG. 3A the instrument tip willrotate to the right (clockwise from the point of view of the proximalend of the instrument 35) as the actuator element 49 is progressivelymoved axially towards the instrument tip 37.

Where the instrument tip 37 is biased towards the initial position asdiscussed above, the rotation of the instrument tip 37 is against therotational bias and leads to energy being stored in the biasing element(e.g. spring 43). Thus, a force needs to be maintained on the actuatorelement 49 to overcome the rotational bias to keep rotating theinstrument tip 37, otherwise the rotation bias will act to return theinstrument tip 37 to its initial rotational orientation and consequentlythe actuator element 49 will be displaced axially back along theinstrument by the rotation of the raised helical edge 55.

Rotation of the instrument tip 37 continues with progressive axialdisplacement of the actuator element 49 until the distal end of theactuator element 49 passes a distal end of the raised helical edge 55.From then on, further axial movement of the actuator element 49 towardsthe instrument tip 37 does not cause any further rotation of theinstrument tip 37. Where the instrument tip 37 is rotationally biasedtowards its initial position, the raised helical edge 55 acting on theshaft of the actuator element 49, which is unable to move sidewaysbecause the guide part 55 prevents the rotational bias from causing theinstrument tip 37 to rotate. Thus, the rotational bias is unable torotate the instrument tip 37 back to its initial rotational orientationuntil the actuator element 49 is retracted to the point where its distaltip is again in contact with the raised helical edge 55.

The actuator element 49 may comprise a needle of the instrument 35 thatis used for injecting fluid, such as saline, into biological tissue incontact with the instrument tip 37. In known electrosurgical instrumentssuch needles have been provided by being fed down a tube within thetubular housing. Such needles are capable of being moved axially alongthe tubular housing, for example to extend or retract a needle tip ofthe needle at the distal end of the instrument. Thus, the distal end ofthe needle can be used to contact the helical path (cam surface) of theinstrument tip as described above, so that axial movement of the needlecan be used to cause rotation of the instrument tip. Utilising theexisting needle component of the electrosurgical instrument in thisdual-purpose manner removes the need to provide a further actuatorelement 49, and therefore results in a simpler and more efficientelectrosurgical instrument. The orientation of the instrument tip may beunimportant during the injecting process using the needle. The injectionmay be performed first, and then the orientation of the instrument tipmay be controlled during electrosurgery by subsequently retracting theneedle to a point where the tip of the needle contacts the cam surfaceof the instrument tip. Alternatively, the injection may be carried outafter controlling the rotational orientation of the instrument tipduring electrosurgery.

Once the distal end of the needle has passed a distal end of the camsurface, further axial movement of the needle to inject fluid into thetissue will not affect the orientation of the instrument tip. Afterbeing used for injecting fluid into the tissue, the needle can beretracted until its tip is in contact with the cam surface (raisedhelical edge 55), and the needle can then be moved in either axialdirection to control clockwise and anticlockwise rotation of theinstrument tip 37.

In one embodiment, the helical path (cam surface) is configured (e.g.its position and/or length and/or pitch are set) so that when the distalend of the actuator element passes the distal end of the helical paththe instrument tip is oriented with the actuator element positionedadjacent a side surface and/or a bottom surface of the instrument tip.This may be an advantageous position for the actuator element to bepositioned, particularly where the actuator element is a needle of theinstrument as described above.

When the actuator element 49 is retracted progressively back along theinstrument 35, the biasing force pressing the raised helical edge 55into contact with the distal end of the actuator element 49 causes theinstrument tip 37 to progressively rotate, in the opposite direction tobefore, back towards its initial orientation. Thus, the rotationalorientation of the instrument tip 37 can be easily and accuratelycontrolled and returned to its initial position when the actuatorelement 49 is retracted.

Of course, the same rotation actuation mechanism described above can beused with different types of rotatable connection, for example with theflexible transmission line rotatable connection illustrated in FIGS. 2Aand 2B and described above (this configuration is discussed below inreference to FIG. 7). Furthermore, the rotation actuation mechanismdescribed above can be used with other types of rotational biasing.

In some embodiments it may be unnecessary to provide the rotational biasto return the instrument tip to its initial rotational orientation.Instead, the interaction between the actuator element and the instrumenttip may be such that axial movement of the actuator element away fromthe instrument tip causes the instrument tip to rotate, in the oppositedirection to before, back towards its initial rotational orientation.For example, the actuator element may comprise a follower in the form ofa protrusion that is received in a helical channel formed in theinstrument tip and that travels along (follows) the helical channel, sothat axial movement of the actuator element in either direction causesrotation of the instrument tip in a clockwise or anticlockwisedirection.

FIGS. 6 and 7 show examples of instrument tips used in embodiments ofthe present invention in more detail. In FIG. 6, the cam surface (raisedhelical edge 55) is exposed and is therefore visible. In contrast, inFIG. 7 the cam surface (raised helical edge 55) is enclosed in a hull ofthe instrument tip and is therefore not visible. However, an exit hole57 at a distal end of the raised helical edge 55 through which theactuator element can protrude from the end of the instrument tip isvisible in FIG. 7. The exit hole 57 is adjacent a side surface of theinstrument tip, so that the actuator element (e.g. a needle) will exitthe instrument tip adjacent the side surface of the instrument tip. Aseal may be provided in or around the cam surface and/or exit hole 57 toprevent the ingress of fluid into the tubular housing.

In both the embodiments of FIGS. 6 and 7 the instrument tips haveaxially extending shaft or shank portions 59 for being received in adistal end of a tubular housing, as discussed above.

FIG. 8 is a schematic illustration of an electrosurgical instrumentaccording to an embodiment of the present invention. Many of thefeatures shown in FIG. 8 have been described in detail above, so only aconcise description of those features is repeated here. It should beunderstood that the specific properties of the features shown in FIG. 8may be the same as the specific properties of the corresponding featuresdescribed above in relation to FIGS. 1 to 7.

In FIG. 8 the instrument tip 61 has the configuration shown in FIG. 6,with a cam surface (exposed raised helical edge 63) formed on a part ofthe external surface thereof.

The instrument tip 61 is fixed to a coaxial feed cable 65 for conveyingradiofrequency energy and/or microwave frequency energy to theinstrument tip. An inner conductor 67 of the coaxial feed cable 65protrudes from a distal end of the coaxial feed cable 65 to contact afirst conductive element on an upper surface of the instrument tip 61.Similarly, an outer conductor of the coaxial feed cable 65 is connectedto a second conductive element on a bottom surface of the instrument tip61.

The instrument tip 61 and the coaxial feed cable 65 are received withina tubular housing 69, shown as being transparent in FIG. 8 for ease ofunderstanding.

The instrument tip 61 is rotatably mounted in the distal end of thetubular housing 69 so that the instrument tip and the coaxial feed cable65 can rotate relative to the tubular housing 69. This is achieved by ashaft of shank portion of the instrument tip 61 being rotatably receivedin the distal end of the tubular housing 69.

The coaxial feed cable 65 is rotatably connected to a further coaxialfeed cable 71 by a rotatable connection 72, such as that illustrated inFIGS. 1A to 1D, which allows rotation between the coaxial feed cable 65and the further coaxial feed cable 71 while allowing the transmission ofradiofrequency energy and/or microwave frequency energy there-between.Thus, the instrument tip 61 and coaxial feed cable 65 can be rotatedwithin the tubular housing 69 relative to the further coaxialtransmission line 71.

The cam surface/raised helical edge 63 is positioned to be contacted bya distal end of a needle 73 of the instrument when the needle 73 ismoved axially along the instrument towards the instrument tip 61. Thus,axial movement of the needle 73 towards the instrument tip 61 so that adistal end of the needle contacts and applies force to the raisedhelical edge 63 causes rotation of the instrument tip 61 as described indetail above.

The needle 73 is configured for injecting fluid into tissue adjacent theinstrument tip 61.

The needle 73 is slidably received in a needle guide tube 75 whichpasses along a slot 77 in a guide ring 79 that is fixed to the tubularhousing 69. The slot 77 of the guide ring 79 constrains the movement ofthe needle 73 so that it can only move in the axial direction relativeto the tubular housing 69, and not sideways.

The instrument further comprises a resilient sheath 81, for example madeof silicone, which is fixed to the rotatable distal part and to thetubular housing 69, directly or indirectly. Thus, when the instrumenttip 61 is rotated relative to the tubular housing 69, the resilientsheath is brought under tension and stores energy. The resilient sheaththus acts as a return spring that rotationally biases the distal part(and therefore the instrument tip 61) to return to an initial rotationalorientation when it is rotated away from the initial rotationalorientation, as described in detail above in relation to FIGS. 3A and3B.

In FIG. 8 the needle 73 is shown in a position where it has been movedaxially along the arrangement so that the distal end of the needle 71 isdistal of the distal end of the instrument tip. In this configuration,the biasing force acting to rotate the instrument tip 61 is unable tocause rotation of the instrument tip 61, because the shaft of the needle73 prevents rotation of the instrument tip 61.

FIG. 9 is a sketch of an electrosurgical instrument according to afurther embodiment of the present invention. The mechanism for actuatingrotation of the instrument tip used in this embodiment is the same as inFIGS. 3A to 8 so description thereof is not repeated and the samereference numbers are used. The primary difference in this embodiment isthat the rotatable connection is the same as (or similar to) that shownin FIGS. 2A and 2B. In other words, a rotatable connection is formedbetween the instrument tip 61 and the coaxial feed cable 71 by aflexible transmission line 19 as described above. As in FIGS. 2A and 2B,the flexible transmission line 19 carries the radiofrequency energyand/or the microwave frequency energy from the coaxial feed cable 71 tothe instrument tip 61.

The flexible transmission line 19 is resilient, so that when the needleis displaced axially along the instrument to contact the raised helicaledge/cam surface 63 and rotate the instrument tip 61, the flexibletransmission line 19 is twisted and stores mechanical energy because ofthis twisting. The twisted flexible transmission line 19 then provides arestoring force on the instrument tip 61 that acts to rotate theinstrument tip 61 in the opposite direction back to its initialconfiguration.

The flexible transmission line 19 therefore allows rotation between theinstrument tip 61 and the coaxial feed cable 71 and also acts as areturn spring to return the instrument tip 61 to an initial rotationalposition when the instrument tip 61 is rotated relative to the coaxialfeed cable 71 away from that initial position.

The flexible transmission strip 19 may therefore replace both the secondcoaxial feed cable and the spring in the embodiments illustrated inFIGS. 3A to 8. The other features of this embodiment and thecorresponding advantages may be the same as the other features of theembodiments illustrated in FIGS. 3A to 8.

Of course, in other embodiments a torsion spring may also be providedaround the flexible transmission line to provide the biasing forceinstead of, or in addition to, the biasing force provided by theflexible transmission line 19 in FIG. 9.

FIG. 10 shows an embodiment having an alternative mechanism forcontrolling rotation of the distal part of the instrument. The followingdescription primarily relates to the rotation mechanism. This rotationmechanism may be combined with any of the rotatable connectionsdescribed above in relation to the previously described embodiments, andthis embodiment may have any of the features of the embodimentsdescribed above, where compatible.

The embodiment illustrated in FIG. 10 comprises a main coaxial feedcable 83, a proximal end of which will in practice be connected to agenerator for supplying microwave frequency or radiofrequency energy. InFIG. 10, the distal end 85 of the main coaxial feed cable 83 is notconnected to anything. In practice, the distal end 85 of the maincoaxial feed cable 83 will be rotatably connected to a rotatable distalpart of the instrument by a rotatable connection as described above inrelation to any one of the previously described embodiments. Forexample, the distal end 85 of the main coaxial feed cable 83 may berotatably connected to a distal coaxial cable by a rotatable connectionas illustrated in FIGS. 1A to 1D. The distal coaxial cable may then befixed to an instrument tip, so that the instrument tip and distalcoaxial cable are together rotatable relative to the main coaxial feedcable 83 via the rotatable connection as a rotatable distal part of theinstrument (e.g. as described above).

The embodiment illustrated in FIG. 10 has a tubular sleeve portion 86that surrounds the distal end 85 of the main coaxial feed cable 83. Inpractice, the tubular sleeve portion 86 will be fixed to the rotatabledistal part of the instrument, for example directly fixed to theinstrument tip, so that the tubular sleeve portion 85 rotates togetherwith the rotatable distal part of the instrument. The tubular sleeveportion may alternatively be referred to as a skirt portion or hollowcylindrical portion. In practice, it is not essential for the sleeveportion to have a tubular or cylindrical shape.

In the embodiment illustrated in FIG. 10, rotation of the distal part ofthe instrument, and therefore rotation of the instrument tip, isachieved by causing rotation of the sleeve portion 86 by axiallydisplacing an actuator element 87 that is coupled to the sleeve portion86 as described below. The actuator element 87 is rod-like orcable-like, and for example may be a needle for injecting liquid intotissue adjacent to the instrument tip.

The actuator element 87 is prevented from moving in any direction otherthan an axial direction relative to the main coaxial feed cable 83 by anactuator guide 89 (needle guide). The actuator guide 89 comprises atubular or ring-like member fixed to the main coaxial feed cable 83(and/or to an external housing) that has an axial channel or slot inwhich the actuator is slidably received. Thus, the actuator element 87is able to move only in the axial direction relative to the main coaxialfeed cable 83.

The actuator element 87 has a helical portion 91, wherein the actuatoris formed in, or bent into, a helical shape. The helical portion 91 isarranged around the outer surface of the main coaxial feed cable 83.

The tubular sleeve portion 86 has a follower 93 adjacent its proximalend that follows a helical path defined by the helical portion 91 as theactuator element 87 is moved axially relative to the main coaxial feedcable 83. As shown more clearly in the enlarged view of FIG. 11, thefollower 93 comprises a ring fixed to an inner surface of the tubularsleeve portion 86 that surrounds the main coaxial feed cable 83 and thathas a channel or slot 95 through which the helical portion 91 of theactuator element 87 passes.

The tubular sleeve portion is prevented from moving axially relative tothe main coaxial feed cable 83, for example by one or more axial stops.Therefore, as the actuator element 87 is moved axially, the axialmovement of the helical portion of the actuator through the channel orslot 95 of the follower 93, which is prevented from moving axially,causes rotation of the follower 93, the direction of the rotationdepending on the axial direction of movement of the actuator element 87.Rotation of the follower 93 causes rotation of the tubular sleeveportion 86, because they are fixed together. Furthermore, rotation ofthe tubular sleeve portion 86 causes rotation of the distal end of theinstrument, because the tubular sleeve portion 86 is fixed to the distalend of the instrument, for example by being directly fixed to theinstrument tip. Thus, axial movement of the actuator element 87 causesrotation of the instrument tip, the direction of rotation of theinstrument tip depending on the axial direction of movement of theactuator element 87.

An important difference between this embodiment and the previouslydescribed embodiments is that the interaction between the helicalportion 91 and the follower 93 is such that movement of the actuatorelement 87 in either axial direction causes rotation of the instrumenttip. For example, movement of the actuator element 87 in the distalaxial direction may cause clockwise rotation of the instrument tip,whereas movement of the actuator element 87 in the proximal axialdirection may cause anticlockwise (counter clockwise) rotation of theinstrument tip, or the other way around.

Thus, with this embodiment it is not necessary to provide a biasingmeans to return the instrument tip to a predetermined rotationalposition once it has been rotated by axial movement of the actuatorelement 87, because the instrument tip can instead be returned to aninitial rotational position by moving the actuator element 87 axiallyback to an initial axial position. In other words, the actuator element87 can be used to rotate the instrument tip in either direction.

Suitable electrical connections can be maintained between the maincoaxial feed cable 83 and the instrument tip during the rotation byproviding a rotatable connection between the distal end 85 of the maincoaxial feed cable 83 and the instrument tip, e.g. with a rotatableconnection as described above in relation to any one of the previouslydescribed embodiments.

As shown in FIGS. 10 and 11, an outer sheath may be present to enclosethe main coaxial feed cable 83, actuator 87 and the other componentsillustrated in FIGS. 10 and 11.

An electrosurgical instrument according to a further embodiment of thepresent invention is illustrated in FIG. 12. The embodiment of FIG. 12has a different mechanism for achieving rotation of an instrument tip ofan electrosurgical instrument to the previously described embodiments.

In the embodiment of FIG. 12, an electrosurgical instrument tip 97 isfixed at the distal end of a coaxial feed cable 99, so that theinstrument tip 97 cannot rotate relative to the coaxial feed cable 99.The inner and outer conductors of the coaxial feed cable 99 areconnected to respective conductive elements of the instrument tip 97,for example as described above in relation to the previously describedembodiments.

The coaxial feed cable 99 is located within a tubular housing or sheath101. Bearings 103 are positioned between the coaxial feed cable 99 andthe sheath 101, so that the coaxial feed cable 99 is rotatable withinthe sheath 101. In the embodiment shown in FIG. 12 two bearings 103 areprovided, one adjacent the proximal end of the sheath 101 and oneadjacent the distal end of the sheath 101. However, in other embodimentsthe bearings 103 may be located differently, and/or further bearings 103may be provided. For example, providing additional bearings 103 to thebearings 103 shown in FIG. 12 may ensure smooth rotation of the coaxialfeed cable 99 within the sheath 101, for example when the sheath 101 andtherefore the coaxial feed cable 99 are bent. Without the provision offurther bearings 103, it is possible that in some circumstances thecoaxial feed cable 99 may come into contact with the sheath 101 when thesheath 101 is bent, restricting rotation of the coaxial cable 99 withinthe sheath 101.

The presence of the bearings 103 mean that the instrument tip 97 can berotated relative to the sheath 101 by rotating the entire coaxial feedcable 99 within the sheath 101 relative to the sheath 101. Any suitabletype of bearing may be used as the bearing 103, for example rollingelement bearings that include rolling elements such as ball bearings, orbrush bearings.

A seal may be provided adjacent the distal end of the sheath 101 toprevent the ingress of fluid into the sheath 101.

The bearings 103 may have axially aligned partial circumferential cuts,channels or openings to allow a needle for injecting fluid into tissueadjacent to the instrument tip 97 to be fed along the sheath 101.

In any of the embodiments described above, the instrument tip may be ahalf-wave resonator/half-wave section. In other words, the instrumenttip may have a length that is substantially equal to

$\frac{\lambda}{2},$

where λ is the wavelength of microwave frequency energy having apredetermined frequency in the instrument tip. The predeterminedfrequency may be 5.8 GHz. Thus, the instrument tip may essentially betransparent to the impedance of the tissue load.

With such an instrument tip, an impedance matching section may also beprovided to match an impedance of the tissue load at the instrument tipto the impedance of the coaxial feed cable at the predeterminedfrequency. The impedance matching section may comprise an impedancetransformer. The length of the impedance transformer may besubstantially equal to

${\left( {{2n} + 1} \right)\frac{\lambda}{4}},$

where n is an integer number greater than or equal to zero and λ is thewavelength of the microwave frequency energy in the impedancetransformer at the predetermined frequency. The impedance transformermay match a real part of the impedance of the tissue load to a real partof the impedance of the coaxial feed cable.

The impedance matching section may further comprise a section of coaxialtransmission line between the impedance transformer and a proximal endof the instrument tip. The section of coaxial transmission line may havea length configured to effectively remove a reactive (imaginary) part ofthe impedance of the tissue load. In this case, the impedancetransformer may match a real part of the impedance of the tissue load asmodified by the section of coaxial transmission line to the real part ofthe impedance of the coaxial feed cable.

The impedance of the section of coaxial transmission line may be thesame as the impedance of the coaxial feed cable, for example 50 Ohms.

In an alternative arrangement for matching an impedance of the tissueload at the instrument tip to the impedance of the coaxial feed cable atthe predetermined frequency, a characteristic impedance of theinstrument tip may be substantially equal to a characteristic impedanceof the coaxial feed cable. Furthermore, the distal part may comprise animpedance matching section for matching the characteristic impedance ofthe coaxial feed cable to the impedance of a tissue load in contact withthe instrument tip at the predetermined frequency of microwave frequencyenergy. The impedance matching section may comprise a length of coaxialtransmission line connected to a proximal end of the instrument tip, anda short circuited stub. Again, the short length of coaxial transmissionline may essentially remove a reactive (imaginary) component of theimpedance of the tissue load, and the short circuited stub may thenmatch the remaining real impedance to the impedance of the coaxial feedline.

In an alternative arrangement for matching an impedance of the tissueload at the instrument tip to the impedance of the coaxial feed cable atthe predetermined frequency, the impedance matching may be achieved by atwo or three stub tuner.

1.-50. (canceled)
 51. An electrosurgical instrument for applyingradiofrequency energy and/or microwave frequency energy to biologicaltissue, the instrument comprising: a distal part comprising aninstrument tip for applying radiofrequency energy and/or microwavefrequency energy to biological tissue, wherein the instrument tipcomprises a first conductive element and a second conductive element; acoaxial feed cable comprising an inner conductor, a tubular outerconductor coaxial with the inner conductor, and a dielectric materialseparating the inner and outer conductors, the coaxial feed cable beingfor conveying radiofrequency energy and/or microwave frequency energy tothe distal part; wherein: the inner conductor is electrically connectedto the first conductive element and the outer conductor is electricallyconnected to the second conductive element through a rotatableconnection between the distal part and the coaxial feed cable thatallows rotation of the distal part relative to the coaxial feed cableabout a central axis of the distal part; the instrument comprises anactuator for rotating the distal part in a first rotational directionrelative to the coaxial feed cable; the instrument comprises a tubularhousing in which the coaxial feed cable is received; the distal part isrotatably mounted at a distal end of the tubular housing; the instrumentcomprises a biasing element configured to rotationally bias the distalpart in an opposite second rotational direction when the distal part isrotated in the first rotational direction; and the biasing element isconnected to the distal part and to the tubular housing.
 52. Theelectrosurgical instrument according to claim 51, wherein the biasingelement comprises a spring or a resilient sleeve.
 53. Theelectrosurgical instrument according to claim 51, wherein the instrumentfurther comprises a stop element configured to prevent rotation of thedistal part in the second rotational direction when the distal partcontacts the stop element.
 54. The electrosurgical instrument accordingto claim 53, wherein the stop element is connected to the tubularhousing.
 55. The electrosurgical instrument according to claim 51,wherein the distal part comprises a second coaxial feed cable comprisinga second solid inner conductor, a second tubular outer conductor coaxialwith the second inner conductor, and a second dielectric materialseparating the second inner and outer conductors, the second coaxialfeed cable being for conveying radiofrequency energy and/or microwavefrequency energy to the instrument tip.
 56. The electrosurgicalinstrument according to claim 51, wherein: the instrument comprises anactuator element for rotating the distal part relative to the coaxialfeed cable; the actuator element is configured to be moved axially alongthe instrument; and the distal part comprises an interface forconverting axial movement of the actuator element into rotationalmovement of the distal part.
 57. The electrosurgical instrumentaccording to claim 51, wherein the instrument tip comprises a planarbody made of a dielectric material separating the first conductiveelement on a first surface thereof from the second conductive element ona second surface thereof, the second surface facing in the oppositedirection to the first surface.
 58. The electrosurgical instrumentaccording to claim 57, wherein: the distal part further comprises aprotective hull mounted to cover the underside of the planar body; theprotective hull has a smoothly contoured convex under surface facingaway from the planar body; the planar body has a tapering distal edge;and the underside of the planar body extends beyond the protective hullat the tapering distal edge.
 59. The electrosurgical instrumentaccording to claim 51, wherein a length of the instrument tip issubstantially equal to $\frac{\lambda}{2},$ where λ is the wavelength ofmicrowave frequency energy having a predetermined frequency in theinstrument tip.
 60. The electrosurgical instrument according to claim51, wherein: a characteristic impedance of the instrument tip issubstantially equal to a characteristic impedance of the coaxial feedcable; and the distal part comprises an impedance matching section formatching the characteristic impedance of the coaxial feed cable to theimpedance of a tissue load in contact with the instrument tip at thepredetermined frequency of microwave frequency energy, wherein theimpedance matching section comprises: a length of coaxial transmissionline connected to a proximal end of the instrument tip; and a shortcircuited stub.